Class objects into ArrayList

[Amit kumar]

how to insert class objects into ArrayList,HashSet either of there,

please explain too....

Thanks

[marc weber]

myListOrSet.add(myObject);

[Chad Clites]

There may be a language issue so I may not be understanding your question fully, but putting an object into an arraylist or a set is the same as anything else. If you are putting a string into an arraylist, you would simply use add. Same for a HashSet. For example:

Foo f = new Foo();
ArrayList a = new ArrayList();
Set set = new HashSet();
a.add(f);
set.add(f);

If you want to use generics, then it is only slightly different:

Foo f = new Foo();
ArrayList<Foo> a = new ArrayList<Foo>();
Set<Foo> set = new HashSet<Foo>();
a.add(f);
set.add(f);

[ August 16, 2007: Message edited by: Chad Clites ]

[Amit kumar]

hi Thanks for replying

what i wish to do is that i have created a seperate class .
--------------------------------------------------------------------------

class Person
{
protected String pName;
protected int pAge;
Person( String n,int a)
{
pName = n;
pAge= a;

}
void display()
{
System.out.println(pName + " your age is "+pAge+" ." );
}
}
 
public class PersonDetails {
 
/**
 * @param args
 */
public static void main(String[] args) {
// TODO Auto-generated method stub
    Person personnel = new Person(" ",0 );
personnel.display();


}
 
}

-----------------------------------------------------------------------
i want to use the above to insert the values into the ArrayList
but not able to...............
-------------------------------------------------------------------------

  
import java.util.*;
import com.practiceJava.PersonDetails;  
public class CheckingArrayList {
 
/**
 * @param args
 */
public static void main(String[] args) {
// TODO Auto-generated method stub
ArrayList objArray = new ArrayList<String>();

objArray.add(new Person("Amit",20));

Iterator iObjArray = objArray.iterator();
while(iObjArray.hasNext())
{
iObjArray.next();

System.out.println(objArray);
}


 
}
 
}

Please guide to achieve this
as while running i am getting the hashcode.
[ August 16, 2007: Message edited by: Amit kumar ]

[Abdullah Mamun]

ArrayList objArray = new ArrayList<String>();
objArray.add(new Person("Amit",20));

To make a code type safe you have to use the type parameter in both sides of the assignment. Since you want to add Person object into the ArrayList, the code should be

ArrayList<Person> objArray = new ArrayList<Person>();
objArray.add(new Person("Amit",20));

System.out.println(objArray);

In the println() method you are passing objArray of type ArrayList. Which actually calls the toString() method, returns the hashCode of the object. If you want a meaningful output for each object of the list, then you can achieve it as follows

for(Person p : objArray) {
    p.display(); //display() method is already defined in Person class
    // System.out.println(p); // In this case you should override the toString() method in Person class for a meaningful output
}

[ August 16, 2007: Message edited by: Al Mamun ]

[Manuel Leiria]

Didn't try but I think it works!

import java.util.*;
import com.practiceJava.PersonDetails;  
public class CheckingArrayList {
 
/**
 * @param args
 */
public static void main(String[] args) {
// TODO Auto-generated method stub
ArrayList<Person> objArray = new ArrayList<Person>();

objArray.add(new Person("Amit",20));

Iterator<Person> iObjArray = objArray.iterator();
while(iObjArray.hasNext())
{
Person person = iObjArray.next();

System.out.println(person.display());
}


 
}
 
}
 
    

[ August 17, 2007: Message edited by: Manuel Leiria ]

[Amit kumar]

Thanks and Sorry,

none of the above suggestion provided the output.

infact they are giving compile time error

[Jesper de Jong]

Then tell us exactly what the error message is, that makes it much easier to find out what the problem is...

[Amit kumar]

i am placing the output
this is am receiving from my code

  [Core, Java, [B]com.practiceJava.Person@45a877[/B], 1, 2, 3]  

but with suggestion
i am getting type mismatch error,

Exception in thread "main" java.lang.Error: Unresolved compilation problem: 
The method println(boolean) in the type PrintStream is not applicable for the arguments (void)
 
at com.practiceJava.CheckingArrayList.main(CheckingArrayList.java:48)

[marc weber]

Originally posted by Amit kumar:
...Please guide to achieve this as while running i am getting the hashcode...

Is this what your question really is? How to get output for a Person that's not "com.practiceJava.Person@45a877"?

If that's the question, then the answer is to override the toString method in the Person class. This method is inherited from Object, and you are getting that default behavior. In your Person class, add...

public String toString() {
  return "whatever String you want output for Person";
}